Nowadays, liquid crystal display (LCD) devices are a kind of widely used flat display device. According to different driving modes, LCD devices can be divided into three kinds of twisted nematic (TN) LCD device, vertical alignment (VA) LCD device and In Plane Switching (IPS) LCD device.
The TN LCD device is the firstly developed kind of LCD device. Advantages of such TN LCD device are that it is cheaper and has higher response rate. However, a view angle range of the TN LCD device is narrow. Compared with the TN LCD device, the VA LCD device and the IPS LCD device can provide wider view angle ranges, and therefore become preferred driving modes for display devices with large screens.
However, although the VA LCD device has wider view angle than the TN LCD device, the VA LCD device generally has a drawback that it may generate color washout at its side view angles. In order to overcome the drawback, a conventional method generally is to divide each pixel circuit of an LCD device into two sub-pixels and use suitable circuit designs to make pixel voltages of the two sub-pixels to be different from each other so as to cause the two sub-pixels to generate different luminance. However, referring to FIG. 1, the aforementioned conventional method can effectively limit luminance of the sub-pixels to be about gamma 2.2 only at certain grey levels. It is obvious that such an improving effect is not satisfactory. Therefore, many researchers are still dedicating themselves to relevant researches for improving color washout phenomenon generated at side view angles of flat display panels.